1. Field of the Invention
The present invention relates to a wheel slip ratio correction apparatus for use in antilock brake systems for motorcycles.
2. Description of the Prior Art
In general, the vehicle speed used in an antilock brake system on a motorcycle is an estimated value. This estimated vehicle speed is calculated based on a signal output from wheel speed sensors which are mounted on each wheel, and detect the rotational velocity of each wheel. In other words, the estimated vehicle speed is calculated based on the front and rear wheel speeds.
However, when one or more of the tire diameters differs from the design value, such as when the two tires mounted on the motorcycle have different wheel diameters or when the air pressure in one tire differs from that of another, an apparent speed difference occurs in the speed of the front and rear wheels even when the vehicle is travelling at a constant rate.
The difference between the estimated vehicle speed and the wheel speed may be recognized by an antilock brake control system to indicate slipping of the tires. Thus, the control system determines that slipping occurs due to the difference in tire diameters even though the tires are in fact not slipping. The antilock brake control system therefore operates to cancel out the apparent slipping, causing the brake pressure to be softened during normal driving and creating a potentially dangerous situation.